Bevel gear checking master



Oct. 29, 3.957 S BEAM ETAI- 2,810,965

BEVEL GEAR CHECKING MASTER Original Fil'ed June 3, 1946 2 Sheets-Sheei'l 1 www @m1 2f Oct. 29, 1957 A. SIBEAM ETAL BEVEL GEAR CHECKING MASTER Original Filed June 5, 1946 2 Sheets-Sheet 2 xNvENTORs RLBERT BEAM Qu CLmENcf agmmaon/ him/iw,

ilnited States atent- BEVEL GEAR CHECKING MASTER Albert S. Beam, Detroit, and Clarence B. Stapleton, Royal Oak, Mich., assignors to Vince Corporation, Detroit, Mich., a corporation of Michigan @riginal application yJune 3, 1946, Serial No. 674,152, now Patent No. 2,689,410, dated September 21, 1954. and this application `luly 27, 1954, Serial No.

This invention relates to gear checking and especially to the checking of concentricity and location of pitch cone, runout, backlash and tooth contact or bearing conditions of bevel gears against a bevel gear checking master. This application is a division of our prior copending application entitled Master Gauge for Bevel Gears, Serial No. 674,152, tiled June 3, 1946, now Patent 2,689,410, issued Sept. 2l, 1954. The run-out test covers the composite effect of errors in any gear element, including tooth prole, spacing, concentricity of pitch diameter, helix angle and tooth spirals.

While the use of bevel gears is very common, no satisfactory equipment was formerly available for accurate and conclusive inspection. Hence, the production of bevel gears is usually followed by a mating process in which a particular set of bevel gears is selected to run well together. This sometimes requires a run in period, or even lapping or burnishing in order to get the desired results and, in any event, complicates production, assembly and replacement.

It is the principal object of our invention to overcome this dimculty and to permit the production ot bevel gears within specified tolerances so they can be used in interchangeable assembly by means of improved inspection procedure made possible by the use of our invention.

When a bevel gear checking master is constructed according to our invention, it is not, as in the case of a spur gear checking master, an extremely precise rendering of the gear to be mated to the gear being checked. It is instead a conjugate crown gear corresponding to the basic spherical rack of the production bevel gear being checked. The teeth of this master crown gear may be straight or curved, depending on whether the bevel gear being checked is of the straight, spiral, zerol or hypoid type.

The theory of bevel gears has been well known for many years. We have constructed a bevel gear checking master which represents the theoretical spherical rack or crown gear used as the basis of generating the bevel gear in question; thus, previous difficulties in producing accurate master bevel gears are avoided since the tooth surfaces of a crown gear represent simple geometric elements, such as planes or cones and, therefore, can be accurately produced and readily inspected.

In the case of straight bevel gears, the straight sided tooth of the bevel gear checking master can be produced as easily as the similar straight sided tooth of a straight rack.

It is to be observed that the bevel gear checking master, though in the form of a crown gear, cannot be accurately termed a crown gear because the ratio of its pitch circumference to its circular pitch is not necessarily an integral number. ln the theoretical spherical rack of mating bevel gears, the pitch radius of the rack is established by the shaft angle and the pitch radii of the mating gears. Hence, the pitch circumference of the theoretical crown gear does not necessarily comprise an integral number of circular pitches.

The use of a bevel gear checking master in the form ice of a crown gear allows an arrangement of the checking fixture in which the direction of force exerted on the crown gear by irregularities in the bevel gear is axial and not, as it would be with a master in true bevel gear form, oblique, thus achieving much greater sensitivity in the inspection fixture.

For a better understanding of our invention, reference is made to the accompanying drawings, in which:

Fig. l is a top plan view of a bevel gear checking fixture constructed according to our invention;

Fig. 2 is a front elevation of the fixture shown in Fig. l;

Pig. 3 is a side elevation of the fixture shown in Fig. l;

Figs. 4 and 5 are perspective views of a bevel gear checking master constructed according to our invention; and

Fig. 6 is a diagram illustrating the imaginary common pitch plane of a pair of bevel gears.

1n Figs. 1, 2 and 3, we have illustrated a preferred embodiment of a fixture employing our bevel gear checking master. This embodiment enables the advantages of our checking master to be realized fully, but for special purposes other fixtures have been found suitable. ln it, the checking master 1 is rotatably mounted on an oifset swinging arm 2. The arm 2 is pivoted about the axis 3 at one end and has a locking device 4 at the other end with which it may be precisely located upon the base 5.

The axis of rotation of the checking master 1 is located between axis 3 and locking device 4, and is perpendicular to axis 3. The pitch plane of the bevel gear checking master 1 will normally fall at or near axis 3 by reason of the offset. A boss 9 is located on the arm 2 with a machined face lying in a plane containing axis 3. An indicator 10 is mounted on base 5 in contact with boss 9 to indicate minute movements of arm 2 about axis 3. At the extreme free end of the arm 2, the spring actuated lever 6 urges it to rotate about its pivot axis 3 in the direction to press the teeth of the checking master 1 into mesh with the teeth of the production bevel gear 7 being checked.

This gear 7 is mounted on the slide S so as to be capable of rotation about its axis when the fixture is employed to check the concentricity of pitch cone and runout. Slide 8 is so constructed that the axis of gear 7 intersects the axis of the checking master 1 when arm 2 is fixed by lock 4. The position of the slide 8 on base 5 is set by moving slide S in contact with stop block 8', so that the pitch cone vertex of gear 7 coincides with the vertex of checking master 1 when arm 2 is fixed by lock 4. Slide S is then locked to base 5 in this position by locking device 22. The swinging arm 2 is then allowed to swing freely by releasing locking device 4 so that the face of checking master 1 is pressed forward and its teeth engage the teeth of bevel gear 7 under the inuence of the spring pressed lever 6. Using hand wheel 18 the bevel gear 7 is rotated by hand, carrying with it the checking master 1. The indicator 10 will register, as a plus or minus reading in fractions of an inch, the exact amount of any eccentricity of the pitch cone or run-out of the bevel gear.

It will be observed that a greater degree of sensitivity is obtained by having the indicator 1li in engagement with boss 9 further from pivot axis 3 than the mating teeth of checking master 1 and bevel gear 7'. However, since the movement of boss 9 will be directly proportional to the run-out of gear 7, the indicator 1t) can be calibrated to read directly the actual amount of run-out.

The fixture also carries on base 5 the additional slide 11, bearing the indicator 12 arranged to read the movement of a point on the heel 13 of arm 14 about pivot 15. The arm 14 is carried by pivot 15 on the bracket 16 of slide 11. The toe 17 of arm 14 terminates in a ball point which engages with the teeth of checking master 1. The 

